by Corrado Nai

Often referred to as “the simplest life form on Earth,” microorganisms are powerful tools in industry and biotechnology. Yet they are also still “black boxes”: Between output (e.g. production of a metabolite) and input (e.g. a given species in a specific growth condition) there are many cellular processes that need to be understood and/or optimized.

Synthetic Biology attempts to change this. The aim is to devise and steer cellular processes in a modular fashion. Cellular components and genes are seen as building blocks to assemble at will. The advantages: controlled and optimised bioprocesses, higher yields, less by-products, new biomolecules. The creation of the first synthetic cell was a crucial contribution in this direction.

Microorganisms are powerful biosensors due to their ability to sense intra- or extracellular signals and to respond by adapting their gene activity. Strains were engineered to produce a fluorescent signal with the presence of, for example, an anabolised amino acid. By screening a heterogeneous population of cells for fluorescence intensity, the highest producing strain(s) can be picked up easily.

Computing – i.e. the ability to process and store bits of information – is a task that bacteria can also do. Bioengineers developed “biocomputers” as therapeutics. Bacteria designed to react to the compresence of two biomarkers in the gut (equivalent to AND operations in computers) modify their DNA and switch on a fluorescent gene. After passing into the body of a sick person with both biomarkers, the fluorescent biocomputers reveal the health status of the patient.

Biotechnological progresses are largely due to the genetic, physiological and morphological versatility of microorganisms. It is here worth noting that the widely used CRISPR/Cas system stems from the immune system of bacteria. So please – don’t call them simple.

Further selected references:
[1] Hutchison III et al. (2016), Science 351(6280):aad6253, doi: 10.1126/science.aad6253.
[2] Meyer et al. (2016), Fungal Genetics and Biology 89:1-2, doi: 10.1016/j.fgb.2016.02.006.
[3] Nødvig et al. (2015), PLoS ONE 10(7):e0133085, doi: 10.1371/journal.pone.0133085.